The invention relates to a draft protection device for a balance, wherein the draft protection device encloses a weighing compartment surrounding a weighing pan and has at least one opening that can be closed by a window. A balance of this type is used primarily in laboratories.
A draft protection device which is disclosed in EP 1 367 372 A1 has a draft-deflecting body consisting of at least two panel elements partially surrounding the weighing compartment of a balance in which the weighing pan is arranged. The body is designed to be handled as a separate part which can be set on the balance in at least two different positions, providing in each of the different positions at least one opening for access to the weighing compartment. The user can position the body in such a way that the respective openings associated with the different positions allow access to the weighing compartment from different directions. The body can be arranged either immediately on a balance housing containing the weighing cell and associated electronics, or it can be arranged on a base which can be set in place on the balance housing. In the latter case, the base forms the floor of the weighing compartment. As a further element of the draft protection device, the base can be equipped with at least one fixed wall which can, for example, form the rear wall of the weighing compartment.
A balance that is described in EP 1 351 041 A2 has a draft protection device with at least two slidable walls for opening and closing the weighing compartment, wherein the arrangement includes a slidable connector body that serves to connect slidable walls that are not bordering on each other. The concept further includes push handles that are designed for coupling or releasing the connection of one slidable wall to another slidable wall, or of a slidable wall to the connector body. A push handle of this kind is formed of handle elements cooperating with each other as a pair, where the respective elements of a pair are attached to adjacent slidable walls, or to the connector body and a wall that is adjacent to it, and where each of the elements of a pair by itself is designed as a handle for sliding the respective wall or the connector body. A first element of each pair is configured with a recess into which the second element can be folded by a swivel motion of the first and/or second handle element so as to couple the handle elements together into a pair, wherein the pair of elements together in their combination as a push handle have an outside contour shape and size essentially equal to the first handle element with the recess.
A cylindrical draft protection device for a balance which is disclosed in U.S. Pat. No. 4,798,250 consists of at least two wall segments, with all of the wall segments being movable relative to each other by means of a motor. The wall segments can be moved individually, or they can be coupled to each other so that they move synchronously.
A draft protection device with movable wall elements that can be moved by a motor is described in U.S. Pat. No. 5,058,692. The motor can be operated with at least two different speeds, so that an individual wall element of the draft protection device can be moved fast in an initial phase of opening or closing, and slower in a second phase prior to reaching a programmable end position.
Another balance with a draft protection device is described in EP 0 556 473 A1, wherein at least one of the openings of the draft protection device can be closed by a window which is divided into at least two window sections that are guided along their travel path by a pair of parallel track grooves running next to each other. Attached to the edges of the window sections are take-along devices, so that when a first window section is moved, the second section of the same window will be dragged along. This concept prevents the problem where a significant portion of a window panel protrudes beyond the balance housing or can even get jammed in its track when the access portals of the draft protection device are completely opened. In the open condition of the weighing compartment, the window sections lie stacked on each other or are positioned next to each other.
The latter arrangement of a window in a balance according to EP 0 556 473 A1, where one window section automatically drags along a further window section by means of take-along devices, creates a problem with the jolts from the abrupt starting and stopping of the further window section at the moment when the take-along devices of the respective window sections come into contact with each other.